LACTATE DEHYDROGENASE IN THE RETINA OF THE GUPPY 



765 



■■' :»f the retina do not stain at ail, or at most very faintly. Also remnants of skin 

 nd eye muscles, adhering to the eye, did not take up the stain which indicates 

 hat inhibition is effective (fig. 5). 



Fig. 4. Fig. 5. 



Photomicrograph of Lebistes retina (kryostat Photomicrograph of Lebistes retina (kryostat 

 section) stained for lactate dehydrogenase acti- section) stained for E-isozyme activity. 

 vity (Incubation médium: 30 mg DPN, 15 mg (Incubation mixture: same as for fig. 4, but 

 nitroblue tetrazolium, 10 mg PMS, 3 ml sodium 3 M urea added.) 



lactate (0.05 M), 8 ml phosphate buffer (0.1 M, 

 pH 8.4). Distilled water added to final volume 

 of 30 ml. Incubation time: 15 min. at 37° C). 



The photoreceptors of Lebistes show a very complex arrangement. Three 

 différent kinds of cônes are présent — inner, middle and outer — the last being 

 twin cônes. The cônes are arranged in a regular mosaic pattern, whereas the 

 rods are interspersed at random (Mùller, 1952). A diagram of a generalized 

 photoreceptor is shown in fig. 6. The relative positions of rods and cônes in dark 

 and light adapted retina of Lebistes are given in figs. 7 and 8. 



When the kryostat sections already referred to, are viewed with oil immersion, 

 it is évident that the LDH activity is most pronounced in the inner segments 

 (ellipsoids) of ail three types of cônes. In the light adapted eye, the outer segments 



